For what it's worth, I'm thinking of some version of this for my upcoming game's modding tools, although the backend processing will be on a web server unlike this demo, and there is much more of an AI agent focus.

This is pretty much exactly https://anvil.works (I'm a founder). The full-featured language is Python (both server and client side). Hit Publish and we'll host it for you (database included), or git-clone it and self-host.

There are a bunch of escape hatches if you want to get to the lower level platform (eg use JS libraries, or express a particular piece of styling in HTML+CSS), but the core experience is very VB-like: drag, drop, edit properties, run code on events.